This study will compare the hypolipidemic effects and influence on lipoprotein and cholesterol metabolism gemfibrozil, simvastatin and atorvastatin in patients with type III hyperlipidemia. After a 4 week dietary baseline, patients will be treated in a random sequence with gemfibrozil (1,200 mg/day), simvastatin (40 mg/day) or atorvastatin (10 mg/day or 80 mg/day) each for 8 weeks; efficacy, metabolic effects and safety will be evaluated on each regimen.